Modify metadata generation script and source code

[kongty]

This PR has these changes

parse_design_meta.py

1. Use json_dump instead of pprint to follow the json format
2. *.bs is not saved in the same directory as .place file. Instead, search for *.bs in the bin directory.
3. Remove bin/ from the testing fields.
4. Add fix to clkwrk assertion error

CodeGen_Clockwork_Target.cpp

1. Store interleaved_input/output as a vector of string, instead of just string.